It is known in the art to form one image by the fusion of a plurality of medical images. For example, a technique for the fusion of a computed tomography (CT) image and a positron emission tomography (PET) image is known in the art. According to this technique, an opacity curve and a color map based on measurements are set for each pixel of the CT image. Similarly, the opacity curve and color map are set for each pixel of the PET image. After this processing, the two images are subjected to fusion.
By the image fusion processing, a medical doctor can obtain both morphologic information of the CT image and functional information of the PET image from one image. According to the image fusion processing, however, a region that does not have to be observed may also be subjected to fusion. For example, an affected region shown in the PET image may overlap a bone region shown in the CT image. In such a fusion image, the information may be congested, and a region of interest (ROI) may not be observed easily.
As described above, a fusion image obtained by the fusion of a plurality of images according to the existing technique may not allow easy interpretation of images.